The Bacch-SP 3D Sound Experience

Princeton physics professor Edgar Choueiri is a suave handsome man. He is also a sophisticated art collector, and when he joins you for dinner, the IQ at the table rises dramatically. For his regular day job, he designs plasma rocket engines. Last, but not least, he is the mind and force behind Bacch-SPa developing company engaged in leading edge virtual reality studies. Dr. Choueiri's audio research focuses on the experience of recorded sound as a fully three-dimensional experience. When Dr. Choueiri gets you in his listening room, in front of his speakers (or anywhere else around the room), prepare to be amazed.

The Doctor's magic 3D experience begins while a pair of tiny in-ear microphones are calibrating the system to compensate for the dimensions of your ear canals, the shape of your outer ears, and your location in the room. This information is what enables the individualized crosstalk cancellation filters to do their job. Interaural crosstalk, where the sound intended for the left ear also reaches the right, and vice versa, is what makes our experience of stereo music playback, diffuse, inconsistent, often tonally skewed, and the soundstage limited to between the speaker positions. Working like a stereopticon, Edgar's Bacch-SP provides up to a 32dB reduction of interaural crosstalk, not with headphones, but with everyday stereo loudspeakers. And without the coloration that previous solutions, like a physical barrier between the ears, are plagued by.

In addition, as the system can be calibrated for a range of listener positions, the Bacch-SP system uses an infrared camera to track the listener's head position and make real-time adjustments to compensate for the change in the listening sweet spot. In fact, once the system is properly calibrated (which takes only a minute), the listener will experience true 3-D sound even as he or she walks about the room (imagine being able to change your seat at a live concert) and . . . you can even place the speakers next to each other or anywhere in the room and the effect will not be lost!

The price (including infrared tracking cameras, microphones, and a dedicated iPad controller) is $54,000. But this is only the start, in a few years our children will be swimming with the Little Mermaid and racing at Monte Carlo.

John Atkinson Comments: I have not been impressed by earlier attempts at crosstalk cancellation. The result seemed unstable, colored, and was limited to such a small sweet spot that it was impracticable for a comfortable listening experience. But after Edgar Choueiri had calibrated the system for my ears and listening position, and played back some binaurally recorded music over a pair of KEF LS50s reinforced by a subwoofer, I was impressed. Not only did the soundstage now wrap almost to my sides and was not affected by my moving my head from side to side and back and forth, what I found most convincing was that the ambience, the reverberation on the recordings, was now a stable, solid halo around the performers, just as it is in reality.

I played some of my own stereo hi-rez recordings, by plugging the TosLink output of my Astell&Kern AK100 portable player into the Bacch-SP processor and heard the same effect: a stable soundstage no longer anchored to the speaker positions and extended almost to my sides. This is a major step forward in sound reproduction where the inventive use of DSP decouples what we hear from the physical locations of the loudspeakers.

Michael Lavorgna offers more on this unique technology, including more detailed photos, here.

Jason Victor Serinus adds: I, too, found the wrap-around aspects of this system amazing. What threw me off, however, was the perspective, which replicated the sound “from the microphone’s ears.” On the orchestral and choral recordings I auditioned, which were recorded with main mike(s) positioned close to and above the conducting platform, I may have listened from a similar sonic perspective as would a conductor, but it did not ressemble anything I’ve ever heard from a seat farther back in the orchestra. Thus, I was simultaneously fascinated and puzzled by the experience.

I achieved a bit of this effect by relocating my listening chair to a very near field position with the speakers very far apart (90 degrees) and distant from the walls. Crosstalk was greatly diminished due to speaker width and early room reflections were reduced. Stereo image solidified and bass deepened and tightened. The effect is so strong that I can't go back to the old positions. Of course, it helps that my son moved out and his bedroom is now my dedicated sound room, which no one messes with.

What a perfect product for our times - $54k and it will work for exactly one person at a time.

I remember hearing some InnerSound electrostats at a New York show that did about everything I would want a speaker to do and thinking _they_ had too small a sweet spot, that is, for two or three people sitting abreast at a normal distance from them.

What happens if your personal assistant or personal trainer or personal bond trader moves about the same room while you're listening and interferes with the interaural crosstalk mediation? "Hey, Mamma Cass just got really big!"

What does the Bacch sound like to those unfortunates in the listening room who are not the calibrated scion? Dolphin squeaks? Will it euthanize any animal companions with ultrasonic hearing (compared to humans) who wander into the Bacch activated listening room?

Can the CIA dual purpose it as an indoor laser or drone micro targeting system for home theaters of war? I bet Putin or Assad could be persuaded to become audiophiles if they aren't already....

Let me append a little comment from one who listens regularly to multichannel surround recordings and endorse JA's comments. The effect is both striking and thrilling. In addition, a demonstration track on which David Chesky speaks as he walks from a distance to just a few inches from the listener's left ear shows that this system can convey the perception of proximity as no other I have yet heard. On the other hand, all the demo tracks selected from older and familiar 2 channel materials, while equally impressive, seemed to present the identical audio perspective regardless of the performer, recording venue and recordist.

I'd call this a very promising effort (if one can disregard the price).

Could the Smyth Realiser replicate (to some degree at least) Bacch-SP 3D performance? (given of course a person positioned in the sweet spot has gone through HRTF-measurements done by the units in the consecutive order: Bacch-SP - Smyth Realiser).

Another question: I try to figure out which David Chesky track you are referring to that Prof. Edgar Choueiri used for the demo. Is it from Dr. Chesky's binaural album 'The Ultimate Headphone Demonstration Disc' and if so which track?

Regards, Babak
Founder, Hi-Reality Project
www.Hi-Reality.org

P.S. wish I was there listening to Pink Floyd Pulse in QSound via the Bacch-SP

I do not see how the Smyth Realiser can replicate this since there is no option for the cross-channel cancellation or the EQ filtering. If you want to look into something somewhat similar, ambiophonics (http://www.ambiophonics.org/), particularly the miniDSP implementation.

I do not know what Chesky track that was but you can contact David or Edgar directly for that info.

I thought that once a BACCH-SP system has been properly calibrated for a listener in a particular room, a Smyth Realiser can then be calibrated for him/her, in the same room, by playback of SR's calibration tones via that BACCH-SP system.

In other words, the listener goes through two measurements wearing microphones: first by the BACCH-SP system, then by the Smyth Realiser. Thus, I thought, the properties of crosstalk cancellation filters of the BACCH-SP would be preserved since the Smyth Realiser creates its 'PRIR' (personalised room impulse response) based on playback via the BACCH-SP filters for the listener.

Have I got it wrong?

I haven't thought about how the head-tracking functionality would be affected (or affect the SR's calibration).

By the way, I found two interesting Stereophile articles related to Bacch-SP/binaural:

Ah. I think that I now see what you are suggesting. You want to listen to headphones, not speakers, and retain the performance of the BACCH-SP system, rather than supplant it. If so, it might work as long as you had access to a BACCH-SP system for calibration and then calibrated the SR using that outcome. However, the BACCH-SP system adjusts the filters for the HRTF based on input from its head-tracker and it is not clear if the SR headtracker could replace that function.

Headphones are by their nature close to perfect crosstalk elimination devices. The Smyth realizer solves the problem of creating an external sound field effect for headphones, but in the process also simulates the crosstalk, which isn't necessary for an external effect (although I know some people add crosstalk to their headphone systems on purpose.) I emailed Smyth years ago inquiring about the possibility of using their system to simulate a crosstalk eliminated external speaker listening experience. They said there was no reason it wouldn't work, and to my thinking it would work extremely well, better than any in-room cancellation effort. I suspect it could be done very simply during the calibration phase of for the Smyth system. First set the speakers and listening position in a stereo dipole configuration,with speakers fairly close to each other. When calibrating for the right channel, block any sound from getting to the left ear microphone. When calibrating for the left channel, block any sound from getting to the right ear microphone.
By doing that you will hear through the headphones what seems to be an externalized sound source that sounds like it's coming from a stereo dipole configuration with near perfect crosstalk elimination and no colorations from crosstalk cancellation software. Ideally you'd take it a step further and compare the coloration of the speaker and room to the source signal and cancel all that out as well, but the Smyth Realizer wasn't made with that in mind. It was made specifically to simulate listening to speakers in a room, with room and speaker effects all simulated.
From personal experience, I have found that a dipole stereo arrangement with a physical barrier can be equalized to counter any coloration induced from the barrier. The result is incredible on some recordings, virtually unnoticeable on others. I never heard it make anything sound worse. It is a pain though to have to straddle the barrier and only enjoy the experience from that one location. I also tried digital recursive crosstalk elimination but found the sound quality unacceptable no matter how I adjusted it. I'm sure Bacch is a big improvement with it's customized hrtf and head tracking, and will be reasonably priced soon enough. Combine that with Occulus goggles and you could really feel like you are at the concert hall! Having visual cues that synchronize with the audio cues will make the effect that much better.

I agree with Rick T. Near field listening is a great experience. Try it with the "world's biggest headphones" Acoustat 2 plus 2. Very cool! It is a tweak anyone can try and it costs... NOTHING!! Move your speaker and listening position.. BINGO. If you need to be mobile in the house , buy some good wireless headphones.

I wonder what patents Bose has for its noise cancellation technologies used for headphones and also, I believe, for various military applications? I'd bet if there is any overlap with what Bacch is doing that we'll see another blast from the Bose legal department.